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: U-bolt, Shim, and Driveshaft Tips  ( 5294 )
Jonathan Tee
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V8 because some say "2 heads are better than one"


« : July 13, 2009, 11:58:36 AM »

Quote
What Does A Suspension U-bolt Do?

    * The u-bolts provide the clamping force required to clamp the leaf spring, top plate, axle seat, axle, and bottom plate firmly together.
    * Properly installed u-bolts eliminate any flexing through the center hole. This is critical since stress concentration and flexing in the center bolt hole area will led to rapid leaf breakage in this area.
    * U-bolt torque prevents horizontal forces from shearing the center bolt.
    * Proper clamping of the spring enhances spring stiffness helping to maintain design ride height and desired handling characteristics.

Important U-bolt Notes:


    * Torque values on u-bolts are critical! Please refer to the table below.
    * Tightening u-bolts should be done incrementally- switching frequently to the other legs of the set in a diagonal or criss-cross pattern.
    * U-bolts must be retorqued after 20 miles of use. Loss of initial torque may occur due to settling of the spring stack.
    * The shape of the u-bolt is critical! Square does not substitute for semi round, nor semi round for round, etc.
    * U-bolt rod is rolled, not cut thread. The diameter is specified by thread size, which is slightly greater in diameter than the unthreaded part of the rod.
    * U-bolts should not be reused! The deep nuts are self-locking by stretching the thread. Attempts to reuse u-bolts may result in loss of torque causing breakage of the spring due to flexing in the center bolt area. In extreme cases, shifting of the axle can lead to an unsafe and costly event.
    * Lock washers or ordinary flat washers must not be used with u-bolts. Compression due to the softness of the material may result in loss of torque. Only deep nuts and thick, hardened washers should be used on u-bolts!
    * Husky Spring u-bolt rod is Grade 5 equivalent in 3/8", 7/16", 1/2", and 9/16" diameters and Grade 8 equivalent in 5/8" ,3/4", 7/8" and 1" sizes. We custom bend with 40 different dies in rod diameters from 3/8" to 1". 1 1/8" and 1 1/4" sizes are available in certain prebent sizes.

How to Measure U-bolts

Refer to the picture at right to properly measure the u-bolt

   1. Diameter at the threaded portion (not at the unthreaded part which is smaller!)
   2. Distance between the legs. (Not center to center or not outside to outside.)
   3. Length of one leg measured to inside top.
   4. Shape of bend. (Round, SemiRound, or Square)



Important note: Always retorque newly installed u-bolts after 20 miles of service. If they have lost noticeable torque, retorque again after 1 day. Continue rechecking until the u-bolts hold torque. (Loss of torque value is usually from settling of the stack of components being clamped together) This is a very important practice because loose u-bolts will cause spring breakage through the center hole, possible shifting of the axle with resulting damage and safety issues!

http://www.huskyspring.com/Page.taf?title=U-bolt%20Tips&page=ubolts
« : October 13, 2009, 11:19:07 AM Jonathan Tee »

Jonathan Tee
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V8 because some say "2 heads are better than one"


« #1 : July 13, 2009, 12:15:15 PM »

Also found this snippet:

Quote
Lubricate the U-bolt threads with Never-Seez (or a similar compound) or a synthetic white lead and oil solution. Also lubricate U-bolt washers to reduce drag on the high nuts.

Jonathan Tee
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V8 because some say "2 heads are better than one"


« #2 : August 26, 2009, 11:04:43 AM »

Here is some good info on castor shims.

http://www.4crawler.com/4x4/ForSale/Shims.shtml#StdWidthShim

Quote
Introduction

On leaf-sprung vehicles, shims (or wedges) are often used to modify the angle between the spring perch on the axle and the leaf spring itself. The correction may be needed because of longer spring shackles tilting the pinion out of alignment, or to change from a single-cardan to a double-cardan drive shaft (for increased drive line angle capability), or to correct steering geometry (so your trucks handles better). An alternative to shims is to cut off the spring perches and re-weld new ones on at the corrected angle, but this is a lot of work and requires careful measurement to get things lined up properly.

Anyway, for whatever reason you need a shim, you do need one. And if you need one you probably need an exact angled one, not just the angle or two the shop has. When I needed shims, I found one shop that had 3 and 6, and another that had 4 and 8. All of these shims were aluminum, and not the nice strong billet aluminum, no they were cheap cast aluminum. Cast aluminum can be brittle, and it tends to fatigue or deform over time, and ultimately break. On the rear axle, this can be a pain if it happens on the trail, if it happens on the front axle, this can be downright dangerous...

1. How do I know what angle to make my shims or if I even need shims?
You may get lucky and find someone else (on a web forum or mailing list) who has done a similar modification to their vehicle (that is similar to yours) and find out what angle shim they used for their application. Or you might contact the lift supplier and ask them what angle shim they reccommend for your type of vehicle with their lift installed. Spring manufacturers should be more than happy to supply this information to you. Luckily, the Internet offers a great resource in finding this sort of information.

Short of finding out from someone else what angle shim is needed, the only real way to know is to measure the angles. Since you are even considering adding shims means you have somehow modified your vehicle. Either you have added lift, changed springs, installed longer shackles, moved spring hangers, etc. You need to get some simple measurements to determine if shims are needed and if so, what angle shim is required. For rear axles, you only have the worry about the angle of the pinion in relation to the driveshaft.

How to measure the driveshaft angles:
Depending on the type of driveshaft you are running, the information on how to measure may be found here.

Front axle pinion and caster angle considerations:
For a leaf-sprung front axle, you can use the above measurements, but they only consider the pinion/driveshaft angles. IMHO, you really want to first address steering angles up front (unless you have a trail-only rig) first then worry about pinion angles. Afterall, if you have to choose between having proper steering geometry or a proper pinion angle (so that you can use 4WD at speed), I would choose proper steering angle any day? Why? Well if you can't drive the truck in a straight line on the road, having 4WD available at high speed becomes a moot point. I have had bad caster angle on my truck and I can tell you that the term "death wobble" is aptly named! When that front end starts hopping all over the road and seems to get progressively worse as you drive is not fun. Give me good solid steering anyway and I can live with a little front driveshaft vibration if I need to use 4WD at higher speeds every once in a while.

So how do you measure the steering caster angle? Best bet is to go to an alignment shop and have them put your truck on the alignment machine and give you a printout of the angles. You'll get a list of toe-in, camber and caster as-measured and they may tell you what the angles should be. If not, consult your owners manual or a good repair manual for your vehicle. As far as what angle to use, its a direct relationship between the number of degrees your caster angle is off and the angle of the shim. For example if your vehicle specs +2 of caster and you are at +5 or -1, you'll need a 3 shim, and just install it in the proper orientation to correct the angle.

On the Toyota front axle, an angle of approx. 6 up (front of perch higher than the back)on the spring perch provides a decent caster angle.
It is not uncommon for the caster angle to be off different amounts on each side of the axle. If so, this means that the axle housing itself is not quite aligned side to side or that it is slightly bent. Best bet is to get a shim to correct the average of the two angle errors. Short of cutting off one steering knuckle and turning it to align with the opposite side, its unlikely that you'll be able to "twist" the housing by using two different angle shims.
    
And if you want to correct BOTH the caster and pinion angles at the same time, the only way to do that properly is to cut and rotate the steering knuckles on the axle to set the proper caster angle and if needed cut and relocate the spring perches (or add shims) to set the proper pinion angle. Here is a writeup on doing this modification on a Toyota solid front axle. On some axles, like the Dana 44, you may find that one of the spring perches is cast into the side of the differential housing and is therefore difficult to modify. In that case, you can either use two shims to change the pinion angle, or cut/relocate the separate perch and then add a single shim to the cast perch to set the pinion angle.
 
Finally, with regards to shimming the front axle. If you have a steering setup with the tie rod and/or drag link above the springs, you need to be sure there is enough clearance over the springs for the steering linkage to pass when adding a shim. Since the shim will add thickness and raise the spring pack off the axle/perch, you'll need to ensure adequate clearance for the thickness of the shim.

CV or double cardan driveshafts:
One complication arises if you are correcting the pinion angle on a CV or double-cardan driveshaft. This is because as you change the pinion angle, the driveshaft angle is also changing. Luckily, it is relatively easy to determine the relationship of the two angles. Basically the angles change by the ratio of the respective lengths of the driveshaft and the pinion extension from the axle center line. Lets say that you measure the distance from the center of the axle to the pinion flange or u-joint yoke and find it is 12" (as measured on a Toyota 8" axle). And lets say the driveshaft measures 60" long from the t-case output flange to the pinion flange. This results in a 1 in 5 ratio, meaning that for every 5 of pinion angle change, the driveshaft angle will change 1/5 of that or 1. This is easy to see if you sketch out the driveshaft and pinions to scale. Since the shim is tilting the axle at it's center line and the pinion sticks out away from that center line, it moves up and down as the angle changes. This means the bottom end of the driveshaft moves up and down by the same amount. But since it is much longer than the pinion length, the angle change is reduced by the ratio of the two lengths.

For a practical example, assume a 20 driveshaft angle and a 10 pinion angle, with a pinion length of 11" and a driveshaft length of 55", again your measurements will likely be different. So this gives a 1:5 ratio of angle changes. So, starting with the 10 difference, we want to end up with the pinion angle 1 - 2 less than the driveshaft angle. So, installing a 7 shim, we would find that the pinion angle would increase from 10 to 17. But at the same time, the driveshaft angle would decrease by 7/5 or 1.4, so it would end up at 18.6 (20 - 1.4). This leaves an angle difference of 1.6, which is within the 1 - 2 target we were shooting for.

2-piece driveshafts (i.e. center support bearing):
For applications with 2-piece driveshafts (i.e ones with a Center Support Bearing - CSB), there is often confusion about what to do about the CSB. Some folks think it is necessary to shim the CSB to correct the driveshaft angle. This is generally not something you want to do. Why? Look at the way the driveshaft is set up. The part from the transmission/transfer case output to the CSB is generally a signle-cardan shaft, It has one or maybe two u-joints on it and generally is run straight at both ends. And since it is a single cardan shaft, the angles at both ends must stay equal for smooth operation. So, if you shim or lower the CSB, you are changing the angle of that shaft and that can lead to alignment issues and vibration. The proper place to shim is at the axle. Only look at the bottom half of the shaft, it is either a single-cardan (u-joint) or double-cardan (CV joint) shaft and you just measure and correct the angles on that part of the shaft. So just treat the bottom half of the 2-piece shaft like any other driveshaft and forget the upper half.

2. How do I figure out how long to make my shims?
You'll want the shims to be about the same size as your spring perch. One way to measure that is to get the distance between the u-bolts (length and width). If the axle is separated from the springs, just measure the spring perch directly. On rare occasions, spring perches can be difference lengths (especially on front axles). Shims can be made different lengths if requested. 4Crawler Offroad does not have a master database of all possible vehicle and axle combinations. By the very fact that you need to add a shim, you have a modified vehicle, the axle may or may not be stock, the perches may or may not be original, and the axle itself may be a hybrid of several different axle components.

So why does the length of the shim matter? It should match the length of the spring perch. If it is too short, the spring may not make contact with the shim along it's full length, since it may hit the end of the perch sticking out past the end of the shim. If the shim is much longer than the perch, the thin end of the shim will likely just bend down around the end of the spring perch and be ineffective. Likewise, for any given angle, the longer the shim, the thicker the material it must be cut from is. Since most applications desire as thin a shim as possible (especially in a spring-under-axle situation), specifying a 6" long shims, for example, where a 4" shim would be sufficient may in fact double the thicknes of the shim.

For example on the Toyota mini-truck axles, the rear spring perch is approx. 4-3/4" long, so the shims would be cut 4-3/4" long for the rear axle. However, some folks replace the stock spring perch with a u-bolt eliminator kit, such as the one AllPro Offroad makes. That kit uses a 6" long spring perch, so that is how long the shims should be.. The front Toyota mini-truck axle spring perches are approx. 5-1/4" long, so that would be the proper length for the front mini-truck axle. Other vehicles probably have varying length spring perches, so don't use the above numbers, grab a tape measure and find out for yourself.

There is no "standard length" for a spring shim or rather there are many standard lengths! 4Crawler Offroad has shims have been made in lengths from 3-1/2" to over 6" long. So bottom line, how long is the spring perch (front-back) on your vehicle's axle (rear or front) to the nearest 1/4" or so. See below for the measurment in question (note this is a modified Toyota rear axle spring perch, stock length is 4-3/4", this one has had 3/8" extensions welded to each end to make it longer). In this case the shim length would be about 5-1/2" long.
« : August 26, 2009, 11:14:05 AM Jonathan Tee »

Jonathan Tee
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V8 because some say "2 heads are better than one"


« #3 : September 17, 2009, 11:38:53 AM »

Measuring Castor with a ruler from http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Measurements

Quote
"Single-Cardan Measurements:
Assuming you have a single cardan driveshaft and want to check if the transfer case output and pinion flanges are close to parallel, just measure the distance between the top and bottom of each flange.
If the dimensions are equal, the two flanges are parallel.
If they are not equal, then each 1/16" difference is equal to 0.9 across the ~4" diameter of the flange (which is the size Toyota uses)
If 0.9 is too confusing for you, call it 1, that is probably close enough for small differences.
Other makes may use different size flanges and some may not use flanges at all,
If no flanges are uses, then an angle finder must be employed to measure the angles
Ideally, you would like the upper measurement to be 1/16-1/8" less than the lower measurement for a bit of static "down-angle". Then, as the axle (and pinion) tilt up under load, the angles will approach parallel. While this measurement can be done with the driveshaft in place, it may be easier to do with it off, in order to get more accurate measurements: "

That said, I measured the distance between the top and bottom yokes and there appears to be between a 1/4" to 5/16" difference between the two. This coincides with the measurement on the wiper plate by the way. Not sure if there is any significance to that but thought I would mention it. Anyway, with this geometry it shows I have a negative caster of approx. 5* if my math is correct.
Does this sound more in line? I know it should be closer to 1* positive but at least it's a starting point. BTW, I did have a guy in the neighborhood look at it, another shade tree mechanic if you will and he says the yoke or axle should face either level or just 1* towards the ground and that way when you encounter obstacles you have a little more flex or room for your drive shaft to manuver before binding.

Jonathan Tee
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V8 because some say "2 heads are better than one"


« #4 : October 13, 2009, 11:41:37 AM »

A few more links on drive line tech:

http://www.4x4wire.com/toyota/tech/driveline/

http://www.4xshaft.com/techinfo.html

http://www.pirate4x4.com/tech/billavista/PR-shaft/

As I have said before, this book has good info on modifications http://cruiserpedia.com/forum/index.php?topic=35.msg251#msg251
« : October 13, 2009, 11:49:34 AM Jonathan Tee »

Jonathan Tee
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V8 because some say "2 heads are better than one"


« #5 : July 17, 2014, 09:56:48 AM »

And a video
« : July 17, 2014, 10:04:24 AM Jonathan Tee »

Keith Richardson
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40's Rule


« #6 : July 17, 2014, 11:37:41 AM »

Thanks JT

Thats the best explanation Ive heard for this yet - magic ! ! !

FJ40-1979 TARSUXGP
FZJ105-1999-TOY100GP
FJ40-1983-LX-ELLEX
FJ Cruiser 2011 BM81KT-GP
KTM 1190 Adv
Ducati Multistrada 1200
KTM 990 SMT
MV Agusta Brutale 920
Kawasaki Z1000J ELR
Honda CB900F

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